The subject matter of this invention relates to orthodontic apparatus and more particularly to intraoral tensioning devices for the purpose of imparting forces to the teeth.
Intraoral elastics have been used by the orthodontic profession for a number of years. The most advanced elastics are generally considered to be those based on urethane elastomers which are molded or extruded into thread, tubes, chain, or small O-rings for ligation.
The primary purpose of the devices (other than the O's) is to move teeth by tensioning the devices between two or several teeth. The polyurethane has been used due to its stability in the oral environment, high strength, and relative high tensile modulus and tear resistance and ease of processing compared to other elastomers such as natural rubber, styrene butadiene rubbers (SBR's), or silicones. A prominent drawback, however, has been the low creep resistance and poor force retention over the normal span between office visits (4-6 weeks). This problem has rendered devices such as the elastic thread, chain or tube, of reduced utility in cases where a steady, long-term force is needed for the best treatment results. Used in such cases now are either steel springs, which can cause considerable patient discomfort, or natural rubber bands which must be replaced by the patient on a daily basis between appointments with the orthodontist.
This invention relates to a novel braided elastic thread which maintains a much greater percentage of its initial force over the normal 6-week period between office visits. The braided thread can be tied into loops and other orthodontically useful shapes to effect tooth movement. The braided form allows these superior properties even where the rubber used to produce each strand of the braid is the same as for the traditional monofilament, molded or extruded product.